The use of intravascular medical devices has become an effective method for treating many types of vascular disease. In general, a suitable intravascular device, such as an intravascular catheter, is inserted into a patient's vascular system, and then navigated through the patient's vasculature to a target site to be treated. Using this method, virtually any target site in the patient's vascular system may be accessed, including the coronary, cerebral, and peripheral vasculature.
Catheters are often utilized for intraluminal procedures, including delivery of medical implants or embolic materials, at a desired location within a body lumen. A catheter typically enters the patient's vasculature at a convenient location, such as a blood vessel in the neck or near the groin. Once a distal portion of the catheter has entered the patient's vascular system, the distal tip may be urged toward the target site by applying an axial force to the proximal portion of the catheter. Catheters having a relatively high level of pushability and kink resistance more effectively communicate this axial force to be “steered” into the target site. Such treatment catheters may need to be navigated a tortuous path through the patient's vasculature, including travel within relatively fragile blood vessels, such as in the brain, and are often required to change direction and to even double back on themselves. Thus, the treatment catheters must be flexible enough to navigate tortuous path, while avoiding damaging the blood vessels through which they travel, in addition to having a relatively high level of torqueability to facilitate the steering process.
It is well-known to employ a guidewire to facilitate the navigation of catheters through the vascular system. Such guidewires include so-called “over-the-wire” and “rapid-exchange” systems. In an “over-the-wire” system, a catheter is introduced into the patient over a guidewire that has been previously introduced into the vasculature; the guidewire extends through the entire length of the catheter, i.e., through an axial lumen of the catheter. In a “rapid-exchange” system, the guidewire extends through only a distal portion of the catheter from the distal tip to a guidewire port located proximal of the distal tip.
A catheter being pushed through a patient's vasculature (whether or not assisted by a guidewire) will usually follow a path of least resistance through a blood vessel, and may end up inadvertently colliding into and/or scraping the inner wall of the vessel being navigated, especially in a tortuous vascular system, and at bifurcated vessels walls, aneurysms, and other anatomical features. Such navigational difficulties can undesirably increase the time needed for positioning the distal end of the catheter at the target location for performing a medical procedure, as well as further increase the risk of trauma or damage to the blood vessels as the catheter is navigated there through.
By way of illustration, FIGS. 1A-B illustrate a method of accessing a bifurcated vasculature 10 using a conventional catheter 30, without guidewire assistance. The bifurcated vasculature 10 includes a main blood vessel 20, a first blood vessel branch 22, a second blood vessel branch 26, and a bifurcated angle 24 between the first 22 and second 26 branches. The catheter 30 distal portion 32 is advanced through the main blood vessel 20 and maneuvered to access a target site within the first blood vessel branch 22. Usually, the catheter 30 advances along a path of least resistance by sliding through the main blood vessel 20, and favoring access to the second blood vessel branch 26 (FIG. 1A). While corrective action may be taken by the attending physician to maneuver the catheter distal portion 32 into the desired second blood vessel branch 26, a distal tip 34 of the catheter 30 may still catch and bump the bifurcated angle 24 (FIG. 1B), which can damage the blood vessel, particularly, a relatively fragile vessel, if in the brain, increasing risk of an undesirable rupture or piercing of the blood vessel walls.
By way of further illustration, FIGS. 2A-C illustrate a method of accessing the bifurcated vasculature 10, in which a guidewire 40 is used to facilitate navigation of the catheter 30. With the guidewire 40 is introduced into the desired first blood vessel branch 22 and the catheter 30 is advanced over the guidewire 40 (FIG. 2A), the catheter distal tip 34 may still catch and cause trauma to the bifurcated angle 24 (FIG. 2B); since the guidewire 40 is not disposed in a concentric configuration within (i.e., is not axially aligned with) the catheter 30. As shown in FIG. 2C the guidewire 40 off-center from the catheter 30, which may force a withdrawal of the catheter 30, with further attempts to advance the catheter distal end tip 34 into the desired first blood vessel branch 22 increasing the risk of trauma to the blood vessel.
Accordingly, it would be desirable to provide a vascular access system for navigating a catheter to a target site in a vasculature in a manner wherein the catheter tends to stay centered within the lumen of a vessel being navigated, thereby minimizing undesired contact with vessel walls and other navigational difficulties caused by misalignment of the catheter.